Easy Starting but dies when given throttle

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Location: Perth Australia

Re: Easy Starting but dies when given throttle

Postby PeterJCorby » Thu Oct 11, 2018 4:39 pm

Hello Folks, Some feedback.
Finally found a ;local expert from the Vintage motor cycle club here in Perth. Keith is is his name. I left my bike with him for a few days and collected it after he called to say it was running, albeit with a leak from around the left barrel. I finally got round to taking it for a rider today and WOW what a difference. The old Matchy certainly goes like the clappers.Keith had mentioned that it idled lumpy, and suspected it may have been cambed at some point. I have to agree as it idles like a bike with a cam, that lumpy braap, braap, braap. sound. When you get her on the road she certainly likes to be ridden hard and fast, does not like putting along at all.
So what did he do that I could not do? He changed out my new plugs for yet another new set, cleaned the points and adjusted the float level. Personally I think he must have access to some kind of magic wand as the difference in this bike is chalk to cheese. Yes the engine is noisy and will have to be rebuild at some not too distant future, but other than that he starts 1st kick and is a whole lot of fun to ride. Motor seems oil tight, though the chain case(primary) allows oil out past the so called seal around the clutch as a horrific rate. May as well drain that case and use chain lube to stop her marking her territory. Other than that HAPPY DAYS!

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Re: Easy Starting but dies when given throttle

Postby ajscomboman » Thu Oct 11, 2018 5:06 pm

[quote="PeterJCorby"Motor seems oil tight, though the chain case(primary) allows oil out past the so called seal around the clutch as a horrific rate. May as well drain that case and use chain lube to stop her marking her territory. Other than that HAPPY DAYS![/quote]


Wouldn't do that. The oil in there is to lubricate the clutch rollers as well as the chain. Using a lube if fine for the chain but it'll be impossible for it to lube the clutch rollers. You'll soon be in for a clutch rebuild.

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Re: Easy Starting but dies when given throttle

Postby PeterJCorby » Fri Oct 12, 2018 2:00 am

:oops: Forgot about the clutch rollers. Having rebuilt that clutch recently I am pretty sure I need to look after it. Will have a look and see if there is perhaps excess oil in the chain case. Also seen a few other posts on here with similar issues and will use their lessons learnt.
Thanks for that.

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Re: Easy Starting but dies when given throttle

Postby g5wqian » Sat Oct 13, 2018 5:50 am

once its started you need to immediately advance it , no need to leave it ticking over retarded .
if its not warmed up a bit it will backfire and spit etc if you open throttle any more than a little bit .
i start mine up and then leave it half choke ticking over for a minute or so then open the choke fully later .

if i try to fire the engine up from being left in garage and its a cold engine and then i want to ride away i will need to use the full choke to start it up , then reduce to half choke once running and then ride away for half mile of so and then can open choke up fully open .

i also have a small bellmouth on the carb which has a gauze on it , this stops you picking up any insects etc that could block something up .

i had played with throttle slide cutaways but the standard slide is best .

needle height is only really for main jet so shouldnt really affect low revs and off idle .

my engine just dont like it from cold if you try starting and running it from cold with no choke at all .

sometimes it can seem that the choke doesnt do anything much , but i had my cable snap a few years ago whilst going 60mph on a main road and it just died instantly on me , luckily i had some cable ties with me and so pulled the bare end of cable out and held it back with the ties to get home .

shouldnt be too much effort for you to get things running right , hope its sorted quick and you enjoy riding out .

ian .

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